Stress responses of carp pond fish stock upon hunting activities of the great cormorant(Phalacrocorax carbo sinensis L.)

In addition to direct predation, cormorants can affect carp pond fish stock through disturbance and wounding of the fish. Fish stress response was evaluated by catch per unit effort (CPUE) using lift‐net sampling. A significantly higher (P<0.001) CPUE was recorded in the littoral region of ponds affected by cormorant visits (43.6 ± 39.6) in comparison with a control pond (CP) without their occurrence (0.9 ± 1.1). Stress indices, spleen somatic index (SSI) and Fulton's condition coefficient (FCC) were evaluated for fish subject to two stress factors, hunting cormorants (HC) and pond harvesting (PH), and compared with levels in fish from the CP. Both SSI and FCC decreased significantly (P<0.05) in PH and HC fish in comparison with the control group, while non‐significant differences were observed in both SSI and FCC indices among the HC and PH groups. Plasma biochemical indices (cortisol, glucose and lactate concentrations) were significantly higher (P<0.01) in the PH group as compared with the HC and CP groups. Concentrations in the HC and CP groups did not differ significantly. Total plasma protein levels were significantly higher (P<0.01) in HC fish compared with CP fish, but did not differ significantly from PH fish.     

Characterization of effects of a long-term wastewater irrigation on soil quality by microbiological and biochemical parameters

Investigations were conducted to evaluate the effects of long-term (up to 100 years) wastewater irrigation on the selected microbiological and biochemical characteristics of a Cambisol and a Haplic Luvisol. The developments of soil oligotrophic and copiotrophic bacteria (including actinomycetes), the total microbial biomass (ATP content), and acitivity of enzymes catalyzing major substrate transformations in soil (β-glucosidase, β-acetyl-glucosaminidase, proteinase, phosphatase) indicated significantly differences between wastewater treated and non-irrigated soil sites. The increases of the individual indices under the effect of wastewater irrigation show that remarkable differences in the microbiological and biochemical parameters of soil quality remained detectable also 20 years after the soil treatment was terminated.     

Dietary isoflavone intake and tissue concentration in cultured sturgeons

A common global trend in modern aquaculture is to reduce or replace fishmeal in fish diets with alternative protein sources, mainly from protein‐rich plants such as soybean; however, plant‐based aquafeeds are a source of substantial amounts of phytoestrogens. Phytoestrogens belong to endocrine‐disrupting chemicals (EDCs) which can negatively interfere with fish reproduction; thus, they should be avoided in sturgeon diet. Therefore, the aim of the study was to evaluate concentrations and the profile of dietary isoflavone phytoestrogens in the two commercial sturgeon diets. A substantial amount of isoflavones, reaching in total from 1.5 to 50 mg/kg of feed, were found in analysed diets. Genistein and daidzein, which are typical constituents of soybean, were the most abundant phytoestrogens in the analysed feeds. Equol, the third most abundant phytoestrogen in the tested samples, was originated most probably from animal components. Additionally, the accumulation of dietary isoflavones in the liver, blood and gonads of two commonly farmed sturgeon species (Acipenser gueldenstaedtii and Acipenser baerii) after long‐term dietary exposure was also assessed. Significant concentrations of isoflavones were found in liver and blood samples of both sturgeon species at 600th and 800th dph, indicating high accumulation of these compounds, which may lead to endocrine disturbance.     

Juvenogens as potential agents in termite control: laboratory screening

Preliminary screening tests of eight juvenogens, fatty acid esters of two parent juvenoid alcohols, showed high juvenilizing effect in the termite Prorhinotermes simplex (Hagen). This effect is manifested by differentiation of termite workers into pre-soldiers, soldiers and/or soldier-intercastes ('soldiers'). Juvenogen 9 was tested with five other termite species: Zootermopsis angusticollis Hagen, Kalotermes flavicollis F, Cryptotermes declivis Tsai & Chen, Reticulitermes santonensis de Feytaud, and R flaviceps Oshima, and showed promising efficacy in force-feeding (FF) as well as in choice bioassays. In the economically important subterranean termites R santonensis and R flaviceps, after application of 0.5 mg ml(-1) in FF experiments ca 57 and 73%, respectively, of workers changed into soldiers. In Zootermopsis angusticollis application of 0.05 mg ml(-1) caused differentiation in 62% soldiers, and 57% soldiers differentiated after topical application of 1 microg of the tested compound per termite. Differentiation of excessive soldiers induced by a juvenile hormone-mimicking compound may cause disruption of the social structure and ultimately the death of the colony.     

Artificial spawning of African catfish Heterobranchus longifilis: differences between the effects on reproduction in females treated with carp pituitary homogenate or Ovopel

The effects of the controlled reproduction of African catfish Heterobranchus longifilis after ovulation stimulation with carp pituitary homogenate (CPH; 4 mg kg^?1; group I) or Ovopel (1/5+1 pellet kg^?1; group II) were investigated. After the application of Ovopel, eggs were obtained from a higher percentage of females than after a CPH treatment (87.5% and 75.0% respectively). The statistically significant (P≤0.05) effect of ovulation stimulator was specified only in the case of the weight of eggs (expressed in grams and in percentage of female body weight), being higher in fish treated with Ovopel compared with CPH‐treated fish (176.02 g, 8.43% and 109.51 g, 5.48%). The quality of eggs expressed in percentage of live embryos after 24 h incubation was higher by 7.5% in fish treated with Ovopel. Latency period did not significantly affect the weight of eggs, fertilization percentage or percentage of living embryos after 24 h of egg incubation. However, the weight of eggs and percentage of living embryos after 24 h incubation were higher in fish spawning after 12 h latency (159.38 g and 85.30%) compared with the weight and quality of eggs obtained from females spawning after 14 h latency (126.15 g and 76.04%).     

Impact of a reduced water salinity on the composition of Vibrio spp. in recirculating aquaculture systems for Pacific white shrimp (Litopenaeus vannamei) and its possible risks for shrimp health and food safety

Tropical shrimp, like Litopenaeus vannamei, in land‐based recirculating aquaculture systems (RAS) are often kept at low water salinities to reduce costs for artificial sea salt and the amount of salty wastewater. Although these shrimp are tolerant against low salinities, innate immunity suppression and changes in the microbial composition in the water can occur. As especially Vibrio spp. are relevant for shrimp health, alterations in the species composition of the Vibrio community were analysed in water from six RAS, run at 15‰ or 30‰. Additionally, pathogenicity factors including pirA/B, VPI, toxR, toxS, vhh, vfh, tdh, trh, flagellin genes and T6SS1/2 of V. parahaemolyticus were analysed. The Vibrio composition differed significantly depending on water salinity. In RAS at 15‰, higher numbers of the potentially pathogenic species V. parahaemolyticus, V. owensii and V. campbellii were detected, and especially in V. parahaemolyticus, various pathogenicity factors were present. A reduced salinity may therefore pose a higher risk of disease outbreaks in shrimp RAS. Because some of the detected pathogenicity factors are relevant for human health, this might also affect food safety. In order to produce healthy shrimp as a safe food for human consumption, maintaining high water salinities seems to be recommendable.     

The impact of climate change on the yield and quality of Saaz hops in the Czech Republic

The impact of climate change on the production and quality of hops Humulus lupulus will depend on future weather conditions in the growing season. Our simulations suggest that hops will be particularly vulnerable to a change in climate. Even with the modest warming so far experienced yields have stagnated and quality declined. Recorded observations show an increase in air temperature which is associated with an earlier onset of hop phenological phases and a shortening of the vegetation period. Simulations using future climate predict a decline in both yields, of up to 7–10%, and α-acid content, of up to 13–32%, the latter a major determinant of quality. The concentration of hop cultivation in a comparatively small region in the Czech Republic makes it more vulnerable than if the crop were grown in more areas with different climates. Thus climate change may gradually lead to changes in the regionalization of hop production. Policy assistance may be necessary for the adaptation of the Czech hop growing industry to changed climatic conditions.     

Juvenile hormone III, hydroprene and a juvenogen as soldier caste differentiation regulators in three Reticulitermes species: potential of juvenile hormone analogues in termite control

The efficacy of juvenile hormone III (JH III) and two JH-mimicking compounds was compared in laboratory experiments with Reticulitermes lucifugus (Rossi), R. santonensis Feytaud and R. virginicus (Banks). Induction of presoldier, soldier and/or soldier-worker intercaste differentiation was taken as positive response to the treatment. The novel juvenogen, a fatty acid ester of a juvenoid alcohol, induced greatest soldier differentiation in all species tested, followed by hydroprene. JH III was less effective. Representatives of three Reticulitermes species showed similar trends in soldier induction rates. Differences in mortality in treatments of termites of the same species from different colonies with the same compound were observed and evidently were caused by differences in the conditions of respective colonies.     

Suitability of a laser rangefinder to characterize winter wheat

In recent years, laser rangefinder sensors have been introduced to the practice and research of agricultural engineering. In research, laser rangefinders have been investigated in horticulture and agriculture. For vehicle-based determination of crop biomass, commercially available laser rangefinders have been analysed and tested to measure aboveground biomass in oilseed rape, winter rye, winter wheat, oats and grassland. Resulting from limited measuring range and fixed beam types, the laser rangefinder models that were investigated only partially met the specific demands for agricultural field and crop conditions. Therefore, a new laser rangefinder scanner (ibeo-ALASCA XT) was chosen. This sensor was specifically developed for driver assistance and autonomous guiding of road vehicles. The scanner was tested in 2008 focusing on the measurement of crop stand parameters in winter wheat under field conditions. The sensor achieved good results with reproducible measurements. Measuring from a stationary vehicle, the standard deviation for the measurements of crop height to characterise the crop stand was less than 3 mm in low, medium, and high biomass areas. The ground speed of the vehicle, ranging from 6 to 24 km h^?1, did not significantly influence the readings. For measurements in front of tractors and self-propelled machines (field sprayers, combines and forage harvesters), the sensor has to scan the crop stands at different inclination angles. It was shown that the inclination angle of the laser beam, which varied from 10° to 80°, significantly influenced the readings. Higher inclination angles resulted in apparent increased heights of the crop stand. For the functional relationship between reflection height levels (95th, 75th, 50th and 25th percentiles, and mean values) and crop biomass density, the coefficient of determination (R²) was greater than 0.9.